a. Field of the Invention
This invention relates to axle shafts. In particular, the invention relates to a method for forming a lightweight axle shaft having variable inner and outer diameters.
b. Background Art
Axle shafts are often subjected to significant loads. Vehicle drive axle shafts, for example, transmit significant torque to the vehicle wheels and are subject to rapid starts and stops in operation. Because of the significant loads that are often imposed on axle shafts, most axle shafts are formed of solid metal to provide sufficient rigidity and strength. Solid axle shafts, however, require a significant amount of material and are relatively heavy. In vehicles, this weight has a negative effect on fuel economy and imposes additional loads on other vehicle components.
Because of the disadvantages associated with solid drive axle shafts, hollow drive axle shafts have been developed as shown, for example, in U.S. Pat. No. 5,213,250, the entire disclosure of which is incorporated herein by reference. Existing methods for forming hollow axle shafts, however, make it difficult to both quickly manufacture multiple axle shafts while also varying the inner and/or outer diameters of the shafts to achieve the objectives of a particular application for the shafts.
The inventor herein has recognized a need for a method for forming an axle shaft that will minimize and/or eliminate one or more of the above-identified deficiencies.